JPH09224354A - Hydraulic drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an engine that is the same as a conventional one and increase the absorption torque of a hydraulic pump and at the same time utilize the engine efficiently, improve fuel consumption, reduce noise, and reduce exhaust gas. SOLUTION: A hydraulic pump 2 is driven by an engine 1 and operation actuators 3 and 4 are driven by pressure oil from the hydraulic pump 2. An electric motor 8 which also plays a role of a generator is provided at the hydraulic pump and the electric motor 8 performs generation and assistance operations by the activation control of a controller 9. The engine 1 is maintained in a constant rotary operation state at a speed corresponding to the minimum fuel consumption rate and constant generated torque corresponding to the constant speed is always transmitted to the hydraulic pump 2. When the required absorption torque of the hydraulic pump 2 is smaller than the constant generated torque, the electric motor 8 is generated at surplus torque and electrical energy is accumulated by an accumulation means 10. On the contrary, when the required absorption torque is larger than the constant generated torque, the electrical energy of the accumulation means 10 is used to assist the electric motor 8 and to supply shortage torque to the hydraulic pump 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device used in construction machines such as hydraulic excavators and wheel loaders, and hydraulic working machines such as forklifts and garbage trucks.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic drive device of this type, an engine and a variable displacement hydraulic pump driven by the engine are provided, and hydraulic oil from the hydraulic pump drives a lower traveling body and various drive parts. It is known to perform the above (see, for example, Japanese Patent Laid-Open No. 62-156440). As shown in FIG. 1, an example of a hydraulic excavator generally includes an engine (1), a hydraulic pump (2) rotationally driven by the engine (1), and a hydraulic pump (2). (5) A control valve (5) for controlling the operation by supplying and controlling the hydraulic oil discharged from the) to various working actuators (3, 4).
A swash plate angle control actuator (6) for controlling the displacement by adjusting the swash plate angle of the hydraulic pump (2), and the actuator (6) is connected to information from the control valve (5). A control valve (7) for performing control based on the control valve. In this hydraulic drive device, the hydraulic pump (2) is controlled by the swash plate angle control actuator (6) to control the displacement of the hydraulic oil of the hydraulic pump (2). )) To supply the required pressure oil, and the engine (1) is provided with a hydraulic pump (2).
The adjustment of the change in the number of revolutions is performed in accordance with the control of the displacement of the engine. That is, as shown in FIG. 2, the hydraulic drive device described above has a horizontal axis indicating the discharge pressure of the hydraulic pump (2), as shown in FIG.
In the orthogonal coordinates defined by the vertical axis indicating the displacement, the maximum displacement (line segment AB) determined by the hydraulic pump (2) itself and the maximum allowable pressure (line segment CD) determined by the entire hydraulic drive system. The operation is performed in a limited region surrounded by the maximum absorption torque (hyperbolic BC) of the hydraulic pump (2) determined by the engine (1) itself. The absorption torque of the hydraulic pump (2) is a torque required for the hydraulic pump (2) to operate the various work actuators (3, 4), and is an output torque of the engine (1). Is the torque absorbed from the This absorption torque corresponds to the discharge pressure of the hydraulic pump (2) multiplied by the displacement per rotation. The product of the absorption torque and the rotation speed is the absorption horsepower of the hydraulic pump (2).

[0003] In the hydraulic drive system including the engine (1) and the hydraulic pump (2), the engine (1) is operated at the time of the standard load operation according to the load of the various operation actuators (3, 4). ) Is operated at the rated horsepower, and the engine (1) is operated at the maximum horsepower during heavy-load work. The state of the engine (1) during the standard load operation and the heavy load operation will be described below.

The absorption torque of the hydraulic pump (2) during the standard load operation is, for example, in a range indicated by Ty1 to Ty2 in FIG. 2, and the required absorption torque of the hydraulic pump (2) during the heavy load operation is shown in FIG. Assuming that Ty3 is in the region beyond the hyperbola BC, the engine (1) rotational speed and the shaft torque, shaft output, and fuel consumption rate at that rotational speed are the performance curves of the engine (1) in FIG. It becomes as shown in. That is, during the standard load operation, the generated shaft torque becomes Tg1 to Tg2, the generated shaft output (generated horsepower) becomes Pe1 to Pe2, and the fuel consumption rate becomes ge1 to ge2, respectively, corresponding to the absorption torques Ty1 to Ty2. In conjunction with this, the engine (1) is operated at the rated speeds Ne1 to Ne2 by the governor controlling the engine (1). FIG. 4 shows this in a time chart. That is, in normal work, the engine (1) generates a shaft torque in the range of Tg1 to Tg2, and the engine speed is controlled in the range of the rated speed Ne1 to Ne2.

[0005] When heavy load work becomes necessary in a part of such standard load work, the amount of work of various work actuators (3, 4) increases, and hydraulic pressure is applied to these actuators (3, 4). It is necessary to supply pressure oil at an absorption torque Ty3 exceeding the maximum absorption torque line (hyperbolic BC) of the pump (2). In this case, the operation of the engine (1) is changed to the maximum horsepower operation in which the engine (1) is operated at the maximum rotation speed Np1 to Np2 by the governor in conjunction with the operation of the throttle lever or the like by the operator, whereby the load on the hydraulic pump (2) is changed. Corresponds to the absorption torque range of Ty1 to Ty2 described above. In response, the load of the engine (1) is such that the generated shaft torque is Tg1 to Tg2, the generated horsepower is Pp1 to Pp2, and the fuel consumption rate is gp1 to gp2. FIG. 5 is a time chart showing the case of the heavy load operation. That is, during heavy-load work, the engine (1)
The hydraulic pump (2) is driven in the limited area (ABCD) by increasing the number of revolutions by setting the hydraulic pump (2) to the maximum horsepower operating state, and the various working actuators are absorbed by the absorbing torque in the limited area (ABCD). Pressure oil required for heavy load work can be supplied to (3, 4).

[0006]

However, in the above-mentioned conventional hydraulic drive system comprising a combination of the engine (1) and the hydraulic pump (2), the driving source mainly for driving the hydraulic pump (2) is the engine (1). ) Causes the following inconveniences.

First, the maximum absorption torque of the hydraulic pump (2) is limited by the maximum generated torque of the engine (1), and the maximum absorption torque of the hydraulic pump (2) is increased to increase the capacity of the hydraulic drive device. It is necessary to change the engine (1) to one having a large torque in order to improve the torque. In this case, when the engine (1) is changed to one having a large torque, not only the size and cost of the hydraulic drive device are increased, but also,
Inconveniences such as deterioration of fuel consumption rate, increase of noise, increase of exhaust gas, etc. are also caused.

Second, since the rated horsepower operation during the standard load operation and the maximum horsepower operation during the heavy load operation are performed by the same engine (1), the fuel consumption rate deteriorates during the heavy load operation.
Inconveniences such as an increase in engine noise and an increase in exhaust gas are caused.

Third, even during a standard load operation, the engine (1) is controlled according to the required absorption torque of the hydraulic pump (2).
Is changed in the range of Ne1 to Ne2, the fuel consumption rate fluctuates accordingly, and the fuel consumption rate deteriorates. Further, the generated shaft torque of the engine (1) is increased or decreased according to the required absorption torque of the hydraulic pump (2), which is not preferable from the viewpoint of effectively utilizing the capability of the engine (1). That is, even if the engine (1) has a torque capacity of, for example, 100 that the hydraulic pump (2) can apply to the hydraulic pump (2), the hydraulic pump (2) is
Not all of 00 are used, but only a part of them, which is not preferable in terms of efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to increase the absorption torque of a hydraulic pump while using an engine having the same capacity as the conventional one. At the same time, it is intended to use the engine with high efficiency and to improve the fuel consumption rate, noise and exhaust gas not only during heavy load work but also under standard load work.

[0011]

In order to achieve the above object, the invention according to claim 1 comprises an engine (1) and a hydraulic pump (2) driven by the engine (1). It is assumed that the operating parts (3, 4) are driven by the pressure oil discharged from the hydraulic pump (2). In this structure, an electric motor (8) that reversibly transmits torque to and from the hydraulic pump (2), and a storage unit (10) that transfers electric energy between the electric motor (8).
And Then, the electric power generation operation of accumulating the electric energy generated by the electric motor (8) by receiving the torque transmission from the hydraulic pump (2) in the electricity storage means (10) and the electricity stored in the electricity storage means (10). By being driven by receiving energy, it can be switched to an assist operation for transmitting torque to the hydraulic pump (2).

In the case of the above construction, the necessary absorption torque of the hydraulic pump (2) absorbed from the engine (1) is determined according to the driving force required in the operating portion, so that the operating portion is under the standard load working condition. When the required absorption torque of the pump (2) is smaller than the maximum generated torque of the engine (1),
The electric motor (8) is switched to the power generation operation, and the surplus torque of the generated torque of the engine (1) is transmitted to the electric motor (8), whereby the electric energy generated by the power generation action is stored in the power storage means (10). ),
It becomes possible to efficiently use the engine (1) as a drive source. On the other hand, during heavy load work in which the required absorption torque is larger than the maximum torque generated by the engine (1), the electric motor (8) is switched to the assist operation, and the electric motor (8) is stored in the power storage means (10). Driven by electric energy stored in the hydraulic pump (2)
Will play the role of a motor for driving the. As a result, the hydraulic pump (2) receives the torque transmission from the electric motor (8), the hydraulic pump (2) is operated with a torque larger than the maximum torque generated by the engine (1), and the hydraulic pump (2) is applied to the operating portion. It becomes possible to supply the pressure oil necessary for performing the load work. That is, it becomes possible to make the absorption torque of the hydraulic pump (2) larger than the maximum generated torque of the engine (1). An induction motor (8) having a power generation function, a synchronous motor (8), or the like may be used as the electric motor (8) capable of switching between the power generation operation and the assist operation. Further, according to such a hydraulic drive system, the engine (1) is switched by switching the electric motor (8) to the power generating operation during the standard load work as described above.
In addition to enabling highly efficient use of torque and switching to assist operation during heavy load work, it is possible to increase the power of the drive of the operating part. 8) is mainly in a power generation operation state, and at night, the electric motor (8) is in an assist operation state, and the hydraulic pump (2) is mainly operated by using the electric motor (8) as a drive source to reduce the noise of the engine (1). It is also possible to plan quiet driving.

According to a second aspect of the present invention, in the first aspect of the invention, an absorption torque detecting means for detecting a necessary absorption torque required by the hydraulic pump (2) for driving the operating parts (3, 4). (11) and a control means (9) for controlling the operation of the electric motor (8). The control means (9) causes the electric motor (8) to generate electric power when the absorption torque detected by the absorption torque detection means (11) is smaller than a predetermined torque set value, while the absorption torque is increased. The assist operation is performed when the torque setting value is larger than the set value.

In the case of the above configuration, the operation of the electric motor (8) is switch-controlled by the control means (9), and when the necessary absorption torque of the hydraulic pump (2) is smaller than the torque set value, the electric motor (8). Is switched to the power generation operation, and the engine (1) is connected to the hydraulic pump (2) in the electric motor (8).
The electric energy generated by the surplus torque of the torque transmitted from is stored in the power storage means (10). On the other hand, when the required absorption torque is larger than the torque set value, the electric motor (8) is switched to the assist operation, and the engine (1) is driven by the torque transmitted from the electric motor (8) to the hydraulic pump (2). It is possible to drive the hydraulic pump (2) with a torque larger than the torque transmitted from the. Therefore, various actions are exhibited depending on the setting of the set value. That is, when the same value as the maximum generated torque of the engine (1) is set as the set value, the driving torque of the hydraulic pump (2) is made larger than the maximum generated torque of the engine (1) by the assist torque from the electric motor (8). It will be possible. That is, the hydraulic drive system can be powered up without changing the engine (1) to a high torque one. Further, when the torque value corresponding to the rotation speed of the minimum fuel consumption rate of the engine (1) is set as the set value, the engine (1 at a rotation speed higher than the rotation speed of the minimum fuel consumption rate of the engine (1) is set. While the operation is avoided and the fuel consumption amount is reduced, the work requiring such a high rotation speed can be performed by the assist torque from the electric motor (8).

According to a third aspect of the present invention, in the second aspect of the invention, the engine (1) is maintained in an operating state of constant rotation at a rotational speed corresponding to the minimum fuel consumption rate of the engine (1) during operation. Control to do so. Then, as the torque setting value in the control means (9), the generated torque value of the engine (1) which is driven at the constant rotation is set.

In the case of the above construction, the engine (1) is always operated at a constant rotation speed at a rotation speed corresponding to the minimum fuel consumption rate regardless of the driving force required in the operating parts (3, 4), A constant torque generated by the rotation operation is always transmitted to the hydraulic pump (2). The generated torque value in the constant rotation operation is set as the torque set value in the control means (9). Therefore, when the required absorption torque in the hydraulic pump (2) is smaller than the set value, Of the constant torque transmitted from the engine (1), the operating part (3,
The absorption torque required for driving 4) is consumed for driving the operating part, and the surplus torque causes the electric motor (8) to generate electric power to store electric energy in the power storage means (10). On the other hand, when the required absorption torque in the hydraulic pump (2) is larger than the torque set value, in addition to the constant torque transmitted from the engine (1), it is supplied from the power storage means (10). The hydraulic pump (2) is operated by the torque transmitted from the electric motor (8) driven by the electric energy. As a result, it is possible to supply the pressure oil required to drive the operating parts (3, 4) while operating the engine (1) at the rotation speed corresponding to the minimum fuel consumption rate. Therefore, regardless of whether the work required in the actuating parts (3, 4) is standard load work or heavy load work, the engine (1) continues to operate at a constant rotation speed at the minimum fuel consumption rate. Therefore, not only the fuel consumption rate is improved, but also the engine (1) noise and exhaust gas are reduced.

Further, in the invention described in claim 4, in the invention described in claim 1 or 2, the electric motor (8) is arranged at an outer peripheral side position surrounding the pump shaft (21) of the hydraulic pump (2). Then, the electric motor (8) and the hydraulic pump (2) are integrally assembled.

Generally, the electric motor (8) is replaced by the hydraulic pump (2).
In order to transfer torque between the electric motor (8) and the hydraulic pump (2), the pump shaft (21) of the hydraulic pump (2) and the rotating shaft of the electric motor (8) are usually combined. Must be arranged in series, and the hydraulic drive device must be relatively long in the direction of the pump shaft (21) of the hydraulic pump (2) and must be increased in size. ) Is disposed on the outer peripheral side of the hydraulic pump (2) and is integrally assembled with the hydraulic pump (2), so that the length of the hydraulic drive device, particularly in the direction of the pump shaft (21), can be reduced. It becomes possible and miniaturization is achieved.

Further, the invention according to claim 5 is the same as claim 4
In the described invention, a cylinder block (22) that rotates integrally with a pump shaft (21) as the hydraulic pump (2)
And a housing (25) covering the periphery of the cylinder block (22). As the electric motor (8), a rotor (81) attached to a position on the outer peripheral surface side of the cylinder block (22) so as to rotate integrally with the cylinder block (22), and the rotor (81)
And a stator (82) attached to the inner peripheral surface side of the housing (25) so as to face radially around the pump shaft (21).

In the case of the above structure, the rotor (81) of the electric motor (8) is connected to the cylinder block (2) of the hydraulic pump (2).
Since the stator (82) of the electric motor (8) is attached to the outer peripheral surface of the housing (25) of the hydraulic pump (2), the electric motor (8) ) Itself is integrally disposed in the housing (25) of the hydraulic pump (2). For this reason,
Heat generated by the operation of the electric motor (8) is generated by the hydraulic pump (2).
The temperature is suppressed by cooling by the oil.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 shows a hydraulic excavator to which the hydraulic drive system according to the embodiment of the present invention is applied. 1 is an engine, 2 is a variable displacement hydraulic pump driven by the engine (1), and 3 is A traveling crawler motor as an operating part, 4 is a cylinder for undulating operation of a boom or the like as an operating part, and 5 is a direction of pressure oil supply to the crawler motor and the cylinder (hereinafter, both are collectively referred to as a work actuator). Control valve for controlling the amount of discharge, 6 is a tilt actuator for changing the swash plate angle of the hydraulic pump (2), and 7 is the operation of the tilt actuator to control the discharge from the hydraulic pump (2). A control valve for controlling the oil flow rate, and 8 is an induction motor that also functions as a generator, and is an electric motor that reversibly transmits torque to and from the hydraulic pump (2). Machine, 9 is a controller as control means for controlling the operation of the electric motor (8) and the control valve (7), 10 is power storage means connected to the electric motor (8) through the controller, and 11 is the hydraulic pump ( 2) Absorption torque detecting means for detecting the required absorption torque. Hereinafter, each component will be described in detail.

The engine (1) is composed of a diesel engine and is governed by a governor (12). The governor (12) receives the rotation speed control signal from the controller (9), and controls the engine (1) to rotate at a rotation speed (see FIG. 9) corresponding to the minimum fuel consumption rate ge1 (see FIG. 9) of the engine (1). Maximum fuel efficiency rpm) Ne1
The engine (1) controls the hydraulic pump (2) so as to maintain the constant rotation operation at a constant rotation speed of the engine, so that the rated shaft torque corresponding to the maximum fuel consumption efficiency rotation speed Ne1. It is made to always transmit Tg1.

As shown in detail in FIG. 7, the hydraulic pump (2) is constructed as an electric motor integrated hydraulic pump (13) in which an electric motor (8) is integrally assembled. That is, the hydraulic pump (2) is connected to the output shaft (14) of the engine (1) via the coupling (15), and the pump shaft (21) is spline-coupled to the pump shaft (21). Cylinder block (22) that rotates integrally with the pump shaft (21), a piston row (23) composed of a plurality of pistons circumferentially built in the cylinder block (22), and a piston row ( It is provided with a swash plate (24) for controlling the stroke amount of 23) and a housing (25) which encloses them to form a closed structure. On the other hand, the electric motor (8) includes a rotor (81) and a stator (82). The rotor (81) is pressed into the outer peripheral surface of the cylinder block (22) and is integrated with the cylinder block (22). The stator (82) is pressed into the inner peripheral surface of the housing (25) so as to radially oppose the rotor (81) and is fixed in a non-rotating state. I have. That is, the electric motor (8) is disposed at a position on the outer peripheral side of the cylinder block (22) centering on the pump shaft (21), and is integrally encased by the housing (25).

In the hydraulic pump (2), the swash plate (24) is tilted by a tilt actuator (6) arranged in the housing (25). By rotating the cylinder block (22) and reciprocating the piston row (23) with respect to (24), the control valve (5) is supplied with a quantity of pressure oil corresponding to the swash plate angle. ing.
That is, in the swash plate (24), the control valve (7) is switched and controlled according to the work load of each work actuator (3, 4) based on the operation amount of the operation lever (not shown) by the operator of the hydraulic excavator, The tilting actuator (6) is tilted according to the actuation amount of the tilting actuator (6), and the piston row (2) is changed according to the change of the swash plate angle.
The stroke amount of 3) is changed so that a predetermined amount of pressure oil is discharged.

The electric motor (8) can be switched between a power generation operation and an assist operation by an operation control signal from the controller (9). That is, the rated shaft torque value Tg1 is preset as the torque set value in the controller (9), and the controller (9) detects the hydraulic pump (2) detected by the absorption torque detecting means (11). When the required absorption torque is smaller than the torque set value, the electric motor (8) is switched to the power generation operation, and when the required absorption torque is larger than the torque set value, the electric motor (8) is switched to the assist operation. ing. More specifically, during the power generation operation, the frequency of the current flowing through the stator (82) is converted by the inverter circuit built in the controller (9) so that the stator (82) acts on the rotor (81). A magnetic force is applied to the rotor (81) driven by the engine (1) at a constant speed,
The rotation of 1) is made to act on the braking side, which corresponds to the difference between the transmission torque Tg1 from the engine (1) to the hydraulic pump (2) and the necessary absorption torque of the hydraulic pump (2). The surplus torque is absorbed by the electric motor (8) to generate electric power, and the generated electric energy is stored in the electric storage means (1
0). On the other hand, when the assist is activated, the stator (8
The magnetic force acting on the rotor (81) from 2) is applied to the rotor (81) which is driven to rotate at a constant speed.
By controlling the electric energy flowing from the power storage means (10) to the stator (82) by the controller (9) so as to act on the side that promotes the rotation of the above, the required absorption torque above the torque setting value. The necessary torque that exceeds this is applied to the hydraulic pump (2). That is, during the assist operation, the electric motor (8) plays a role as a normal drive motor.

The storage means (10) may be composed of a capacitor or the like in addition to the battery. The required absorption torque detected by the absorption torque detecting means (11) is directly detected by a pressure sensor and a swash plate angle sensor normally provided in the hydraulic pump (2), and is also detected by the engine (1) detected from the governor (12). ) May be performed indirectly by a minute change in the number of revolutions.

Next, the operation of the engine (1), the hydraulic pump (2) and the electric motor (8) will be described with reference to FIGS. 8 to 10. The engine (1) has the minimum fuel consumption rate ge1 as described above. Is controlled so that the hydraulic pump (2) is constantly rotated at a constant rotation speed Ne1 corresponding to the rotation speed Ne1, whereby the hydraulic pump (2) is always rotated at the constant rotation speed at the rotation speed Ne1 and the rotation speed Ne1. A constant torque is constantly transmitted at an axial torque Tg1 corresponding to (see FIGS. 9 and 10).

In the range of standard load work (range of line segment ABCD in FIG. 8), each work actuator (3, 4)
The swash plate of the hydraulic pump (2) is tilted in accordance with the work load amount from the engine, and the hydraulic pump (2) absorbs the absorption torque corresponding to the work load amount by the constant transmission torque Tg1 from the engine (1).
Consume from. In this standard load work range, the required absorption torque of the hydraulic pump (2) is smaller than the torque setting value (= shaft torque Tg1), so the electric motor (8) absorbs the excess torque and operates to generate electricity (Fig. Electric energy is stored in the storage means (10) and the hatched portion of the broken line 10).

On the other hand, each of the above work actuators (3,
The work load in 4) is the range of heavy work (line B in FIG. 8).
In the range surrounded by EFC), the necessary absorption torque of the hydraulic pump (2) exceeds the torque setting value, so that the electric motor (8) is assisted by using the electric energy from the electric storage means (10). As a result, a torque (assist torque) corresponding to the shortage of the constant transmission torque Tg1 from the engine (1) is applied from the electric motor (8) to the hydraulic pump (2). For example, if the required absorption torque value of the hydraulic pump (2) is T within the heavy load work range.
If y3, the assist torque (Ty3-Tg1) corresponding to the shortage of the required absorption torque Ty3 with respect to the constant transmission torque Tg1 is applied from the electric motor (8) to the hydraulic pump (2).
(See the solid line hatching portions in FIGS. 8 and 10).

As described above, even in the above heavy load working range, the engine (1) is rotated at the rotational speed N at the minimum fuel consumption rate ge1.
Since it is sufficient to continue operating at e1, it is possible to reduce fuel consumption during heavy load work, engine noise, and exhaust gas amount. In addition, the required absorption torque of the hydraulic pump (2) required for the heavy load work can be secured by the torque assist from the electric motor (8) to reliably perform the heavy load work on each work actuator (3, 4). it can. In addition, torque assist for the hydraulic pump (2) during heavy load work can be performed by electric energy stored during standard load work, and the driving force of one engine (1) can be effectively used with high efficiency. it can.

Further, since the hydraulic pump (2) has a structure in which the electric motor (8) is integrated as described above, the length of the pump shaft (21) can be particularly shortened by adding the electric motor (8). It is possible to reduce the size of the hydraulic drive device as a whole, and to prevent overheating of the electric motor (8) itself by oil cooling with oil on the hydraulic pump (2) side to maintain the performance and improve the durability of the electric motor (8). Can be achieved.

<Other Embodiments> It should be noted that the present invention is not limited to the above-described embodiments, but includes various other embodiments. That is, in the above embodiment,
An example in which the present hydraulic drive device is applied to a hydraulic excavator has been described. However, the present invention is not limited to this, and is applicable to any type in which the operating unit is driven by pressure oil supplied from a hydraulic pump (2). For example, the present invention can be applied to construction machines such as wheel loaders and hydraulic working machines such as forklifts and garbage trucks.

In the above embodiment, the induction motor (8) which also serves as an induction generator is shown as the electric motor (8).
However, the invention is not limited thereto, and a synchronous motor such as a brushless DC motor may be used.

[0035]

As described above, according to the hydraulic drive system of the first aspect of the present invention, when the electric motor (8) is switched to the power generation mode, the hydraulic pump (2) driven by the engine (1) operates. The electric power generated by the electric motor (8) in response to the torque transmission can be stored in the electric storage means (10). On the other hand, when the electric motor (8) is switched to the assist operation, the electric storage means (1
The electric energy from (0) can be used to operate the electric motor (8) to drive the hydraulic pump (2). This makes it possible to use the engine torque with high efficiency and power up the entire hydraulic drive system, and also contribute to reduction of fuel consumption, reduction of engine noise, and reduction of exhaust gas amount. .

According to the invention of claim 2, in addition to the effect of the invention of claim 1, by setting the torque set value to the same value as the maximum generated torque of the engine (1), the hydraulic pump (2 In addition to the maximum torque generated by the engine (1), the drive torque can be increased by an amount corresponding to the assist torque generated by the assist operation of the electric motor (8), without changing the engine (1) to a large torque. It is possible to increase the power of the entire hydraulic drive system. Further, by setting the torque setting value to a torque value corresponding to the rotation speed of the minimum fuel consumption rate of the engine (1), engine operation at a rotation speed higher than the rotation speed of the minimum fuel consumption rate is avoided. Fuel consumption can be reduced, and the engine (1) can be operated at high rotation speed by the assist torque by the assist operation of the electric motor (8) even in heavy load work requiring such high rotation speed. It can be executed without fail.

According to the third aspect of the invention, in addition to the effect of the first aspect of the invention, a torque larger than the torque generated at the rotation speed corresponding to the minimum fuel consumption rate of the engine (1) is required. Even in heavy load work, torque assist can be provided to the hydraulic pump (2) using electric energy generated by surplus torque during standard load work performed with a torque smaller than the generated torque. Thus, the heavy load work can be executed. Therefore, regardless of whether the work required in the operating unit is the standard load work or the heavy load work, the engine (1) can be continuously operated at the constant rotation speed at the rotation speed corresponding to the minimum fuel consumption rate. , Not only improving the fuel consumption rate,
It is possible to reliably reduce engine noise and exhaust gas.

According to the invention described in claim 4, in addition to the effect of the invention described in claim 1, the length of the hydraulic drive device, particularly in the direction of the pump shaft (21), can be shortened,
This makes it possible to reduce the size of the entire hydraulic drive system.

Furthermore, according to the invention of claim 5, in addition to the effect of the invention of claim 1, the electric motor (8) itself is integrally arranged in the housing (25) of the hydraulic pump (2). Therefore, the function of cooling the oil in the hydraulic pump (2) can prevent overheating due to the operation of the electric motor (8).

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a conventional example of a hydraulic drive device.

FIG. 2 is a torque diagram of the hydraulic pump in the case of FIG.

FIG. 3 is a performance curve diagram showing a relationship between a shaft torque, a shaft output, and a fuel consumption rate with respect to the engine speed in the case of FIG. 1;

FIG. 4 is a time chart showing a correlation among a shaft torque, a shaft output, a rotation speed, and a fuel consumption rate during a standard load operation in FIG. 1;

5 is a time chart showing the interrelationship of shaft torque, shaft output, rotation speed, and fuel consumption rate during heavy load work in FIG. 1. FIG.

FIG. 6 is a schematic diagram showing an embodiment of the present invention.

FIG. 7 is an enlarged sectional explanatory view of the electric motor-integrated hydraulic pump in FIG. 6;

FIG. 8 is a torque diagram of the hydraulic pump according to the embodiment.

FIG. 9 is a performance curve diagram showing the relationship between the engine speed and the shaft torque, the shaft output, and the fuel consumption rate in the case of the embodiment.

FIG. 10 is a time chart showing a mutual relationship among shaft torque, shaft output, rotation speed, and fuel consumption rate of the embodiment.

[Explanation of symbols]

1 Engine 2 Hydraulic Pump 3 Crawler Motor, Work Actuator (Actuator) 4 Cylinder, Work Actuator (Actuator) 8 Electric Motor 9 Control Means 10 Storage Means 11 Absorption Torque Detecting Means 13 Electric Motor Integrated Hydraulic Pump 21 Pump Shaft 22 Cylinder Block 25 housing

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H02K 7/14 F15B 11/00 F (72) Inventor Nobuyuki Tani Nishiichitsuya 1-1, Settsu City, Osaka Prefecture No. 1 Daikin Industry Co., Ltd. Yodogawa Works (72) Inventor Atsuhiro Uebayashi No. 1 Nishiichitsuya, Settsu City, Osaka Prefecture Daikin Industry Co., Ltd. Yodogawa Works (72) Inventor Masaaki Suhara No. 1 Nishiichitsuya, Settsu City, Osaka Prefecture Daikin Industry Co., Ltd. Yodogawa Works

Claims (5)

[Claims] An engine (1) and the engine (1)
And a hydraulic pump (2) driven by the hydraulic pump (2).
4) In a hydraulic drive device for driving, an electric motor (8) that reversibly transmits torque to and from the hydraulic pump (2), and an electric storage that transfers electric energy between the electric motor (8). Means (10), wherein the electric motor (8) receives the torque transmitted from the hydraulic pump (2) and stores the electric energy generated in the electric storage means (10), and the electric storage means (10). ), The hydraulic drive device is configured to be switchable between an assist operation for transmitting torque to the hydraulic pump (2) by being driven by receiving the electric energy stored in the hydraulic drive device. 2. The absorption torque detecting means (11) for detecting a necessary absorption torque of a hydraulic pump (2), which is necessary for driving an operating part (3, 4), according to claim 1, and an electric motor (8). ) Control means (9) for controlling the operation of the absorption torque detecting means (1).
When the absorption torque detected by 1) is smaller than a predetermined torque set value, the electric motor (8) is operated to generate electricity, and when the absorption torque is larger than the torque set value, the assist operation is performed. A hydraulic drive device characterized in that 3. The engine (1) according to claim 2, wherein the engine (1) is controlled so as to maintain an operating state of constant rotation at a rotation speed corresponding to a minimum fuel consumption rate of the engine (1) during operation. ), The generated torque value of the engine (1) driven to rotate at a constant speed is set as the torque set value. 4. The electric motor (8) according to claim 1 or 2, wherein the electric motor (8) is arranged at a position on an outer peripheral side surrounding the pump shaft (21) of the hydraulic pump (2), and the electric motor (8) and the hydraulic pump ( 2) A hydraulic drive device characterized by being integrally assembled with. 5. The hydraulic pump (2) according to claim 4, comprising a cylinder block (22) which rotates integrally with the pump shaft (21), and a housing (25) which covers the circumference of the cylinder block (22). The electric motor (8) is provided with a rotor (81) attached to a position on the outer peripheral surface side of the cylinder block (22) so as to rotate integrally with the cylinder block (22), and the rotor (8).
A stator (82) attached to an inner peripheral surface side of the housing (25) so as to face the pump shaft (21) in the radial direction with respect to the pump shaft (21). Hydraulic drive.